Airbags serve to mitigate the kinetic energy of a vehicle occupant in the event of an accident. In the event of an accident, the vehicle occupant becomes immersed in an inflating or already inflated airbag. The controlled escape of the gas from the airbag slows down the motion of the vehicle occupant, preventing or reducing injury. To this end, it is important that the airbag inflate as completely as possible as rapidly as possible. It is problematic, however, that different pressure levels must be built up in the airbag for various occupants with different body weights and body sizes and for different accident sequences. An adapted escape of the gas from the airbag should likewise be provided to account for the different accelerations and forces as a function of the severity of the accident and the constitutions of the vehicle occupants. To this end, a so-called active or adaptive ventilation of the airbag is proposed.
There is known from U.S. Pat. No. 6,648,371 B2 an airbag unit comprising a variable ventilation in which the ventilation characteristic is implemented by a selective displacement of sealing devices for ventilation openings. After collecting sensor data regarding the vehicle occupants and possibly the severity of the accident, the required airbag volume and amount of ventilation are calculated to achieve optimum deceleration values for the vehicle occupants. To this end, it is suggested in an example embodiment that within the airbag, a retaining strap fastens a hose-like gas distribution system, which is tucked inwards, to a fastening means. If the airbag is inflated by a gas generator, the retaining strap is released as a function of sensor data, and the gas distribution section turns outwards and discharges the gas into the environment at a fixed time. To this end, a fastening frame clamps the airbag to a base plate, upon which the gas generator is also fastened. However, the disadvantage to this is the complexity of assembly and the associated high cost because the retaining strap is guided inside the airbag and the airbag is screwed onto the base plate together with the gas generator.